package com.imooc.common.thread;

import java.util.Arrays;
import java.util.Random;
import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.RecursiveTask;

/**
 * Created by deng_wb on 2019/8/17
 */
public class ForkJoinPoolTest {
    static int[] nums = new int[1000000];
    static final int MAX_NUM = 50000;
    static Random r = new Random();

    static {
        for (int i = 0; i < nums.length; i++) {
            nums[i] = r.nextInt(100);
        }
        System.out.println(Arrays.stream(nums).sum());
    }

    static class AddTask extends RecursiveTask<Long>{ //递归任务
        int start,end;
        AddTask(int start,int end){
            this.start = start;
            this.end = end;
        }


        @Override
        protected Long compute() {

            if (end -start<=MAX_NUM){
                long sum = 0L;
                for (int i = start;i<end;i++){
                    sum += nums[i];
                }
                System.out.println("from: "+start+" to: "+end +" = "+sum);
                return sum;
            }
            int middle = start +(end - start)/2;

            AddTask subTask1 = new AddTask(start,middle);
            AddTask subTask2 = new AddTask(middle,end);

            subTask1.fork();
            subTask2.fork();

            return subTask1.join()+subTask2.join();
        }
    }

    public static void main(String[] args) {
        ForkJoinPool fjp = new ForkJoinPool();
        AddTask task = new AddTask(0,nums.length);
        fjp.execute(task);
        long result  = task.join();
        System.out.println(result);

    }
}
